linux-kernel - Re: [PATCH v2 04/14] clk: st: Adds Flexgen clock binding

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Message-ID: <20140630092658.GR7262@leverpostej>
Date:	Mon, 30 Jun 2014 10:26:58 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Gabriel FERNANDEZ <gabriel.fernandez@...com>
Cc:	"mturquette@...aro.org" <mturquette@...aro.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"kernel@...inux.com" <kernel@...inux.com>,
	Lee Jones <lee.jones@...aro.org>,
	Gabriel Fernandez <gabriel.fernandez@...aro.org>
Subject: Re: [PATCH v2 04/14] clk: st: Adds Flexgen clock binding

On Fri, Jun 27, 2014 at 02:25:01PM +0100, Gabriel FERNANDEZ wrote:
> A Flexgen structure is composed by:
> - a clock cross bar (represented by a mux element)
> - a pre and final dividers (represented by a divider and gate elements)
> 
> Signed-off-by: Gabriel Fernandez <gabriel.fernandez@...aro.org>
> Acked-by: Peter Griffin <peter.griffin@...aro.org>
> ---
>  .../devicetree/bindings/clock/st/st,clkgen.txt     |  5 +++
>  .../devicetree/bindings/clock/st/st,flexgen.txt    | 48 ++++++++++++++++++++++
>  2 files changed, 53 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/clock/st/st,flexgen.txt
> 
> diff --git a/Documentation/devicetree/bindings/clock/st/st,clkgen.txt b/Documentation/devicetree/bindings/clock/st/st,clkgen.txt
> index 427bad8..78978f1 100644
> --- a/Documentation/devicetree/bindings/clock/st/st,clkgen.txt
> +++ b/Documentation/devicetree/bindings/clock/st/st,clkgen.txt
> @@ -32,6 +32,10 @@ address is common of all subnode.
>  		vcc_node {
>  			...
>  		};
> +
> +		flexgen_node {
> +			...
> +		};
>  		...
>  	};
>  
> @@ -45,6 +49,7 @@ Each subnode should use the binding discribe in [2]..[7]
>  [5] Documentation/devicetree/bindings/clock/st,clkgen-prediv.txt
>  [6] Documentation/devicetree/bindings/clock/st,vcc.txt
>  [7] Documentation/devicetree/bindings/clock/st,quadfs.txt
> +[8] Documentation/devicetree/bindings/clock/st,flexgen.txt
>  
>  
>  Required properties:
> diff --git a/Documentation/devicetree/bindings/clock/st/st,flexgen.txt b/Documentation/devicetree/bindings/clock/st/st,flexgen.txt
> new file mode 100644
> index 0000000..f2d4333
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/st/st,flexgen.txt
> @@ -0,0 +1,48 @@
> +Binding for a type of flexgen structure found on certain
> +STMicroelectronics consumer electronics SoC devices
> +
> +This structure includes:
> +- a clock cross bar (represented by a mux element)
> +- a pre and final dividers (represented by a divider and gate elements)
> +
> +This binding uses the common clock binding[1].
> +
> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> +
> +Required properties:
> +- compatible : shall be:
> +  "st,flexgen"

That looks very vague. Is this a sub-node of a larger block?

Might there be a future flexgen revision that looks different?

> +- #clock-cells : from common clock binding; shall be set to 1.

what does the clock cell represent? Is it just a linear index from 0?

> +- clocks : from common clock binding

This is a completely useless description.

Which clock inputs do you expect clocks for? How many? Are they named?

> +
> +- clock-output-names : From common clock binding. The block has 4
> +                       clock outputs but not all of them in a specific instance
> +                       have to be used in the SoC. If a clock name is left as
> +                       an empty string then no clock will be created for the
> +                       output associated with that string index. If fewer than
> +                       4 strings are provided then no clocks will be created
> +                       for the remaining outputs.

That's a Linux-internal detail, surely?

Why do we even do that?

Mark.

> +
> +Example:
> +
> +	clockgen-d2@...06000 {
> +		compatible = "st,clkgen-c32";
> +		reg = <0x9106000 0x1000>;
> +
> +		clk_s_d2_flexgen: clk-s-d2-flexgen {
> +			compatible = "st,flexgen";
> +
> +			#clock-cells = <1>;
> +			clocks = <&clk_s_d2_quadfs 0>,
> +				 <&clk_s_d2_quadfs 1>,
> +				 <&clk_s_d2_quadfs 2>,
> +				 <&clk_s_d2_quadfs 3>;
> +
> +			clock-output-names = "clk-pix-main-disp",
> +					     "clk-pix-pip",
> +					     "clk-pix-gdp1",
> +					     "clk-pix-gdp2";
> +		};
> +	};
> -- 
> 1.9.1
> 
> 
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